1. Field of the Invention
The present invention relates to an electrical connector for electrically connecting an electronic package such as a ball grid array (BGA) central processing unit (CPU) with a circuit substrate such as a printed circuit board (PCB).
2. Description of the Prior Art
At present, electrical connectors are widely used to electrically connect land grid array (LGA) central processing units (CPUs) with printed circuit boards (PCBs). Such an electrical connector 9 shown in FIG. 6 generally comprises an insulative housing 90 and a multiplicity of terminals 92 disposed in the housing 90. The housing 90 defines a number of passageways 901 each of which receives one of the terminals 92. Referring to FIG. 7, each of the terminals 92 includes a retaining portion 920 with several barbs to interfere with edges near the passageways 901 to secure the terminal 92 in the housing 90, a solder pad 922 extending from an upper portion of the retaining portion 920, an L-shaped connecting portion 925 extending from a lower portion of the retaining portion 920, and a contact beam 926 extending from an upper end of the connecting portion 925. A solder ball 928 is attached on the solder pad 922. An arc portion 929 is formed at a free end of the contact beam 926. The arc portion 929 forms an upper contact point (now labeled) which protrudes towards a bottom surface of an LGA CPU (not shown) with a number of metal pads.
Referring to FIG. 8, in use, the connector 9 is assembled onto a PCB 8 with the solder balls 928 of the terminals 92 contacting pads 80 of the PCB 8. The LGA CPU is attached on the connector, with the metal pads of the LGA CPU corresponding to the arc portions 929 of the terminals 92. The LGA CPU is pressed down, and the metal pads of the LGA CPU abut against the upper contact points of the arc portions 929 of the terminals 92 to deform the terminals 92. The contact beams 926 of the terminals 92 form a vertical force towards the metal pads of the LGA CPU, thereby the terminals 92 electrically contacting the metal pads of the LGA CPU. Thus, the connector 9 electrically connects the LGA CPU with the PCB 8. In above-mentioned operation, compression of the metal pads of the LGA CPU deforms the connecting portions 925 of the terminals 92, such that the upper contact points move in a horizontal direction. Because the metal pads of the LGA CPU has a length in the horizontal direction, displacements of the upper contact points of the terminals 92 are unlikely to affect electrical connections between the terminals 92 and the metal pads.
Recently, with utilization of ball grid array (BGA) CPUs, a shortcoming of the above-mentioned connector 9 appears. Referring to FIG. 8, a BGA CPU has a number of solder balls disposed on a bottom surface thereof. In an assembly of the BGA CPU 7 with a number of solder balls 70 and the connector 9, it is desired that a lower dead point of each of the solder balls 70 abuts against the upper contact point of corresponding terminal 92 of the connector 9. Therefore, the contact beam 926 of each of the terminals 92 provides a vertical force in an axial direction, and connections between the terminals 92 and the solder balls 70 are steady and reliable. However, in use, when the solder balls 70 press the arc portions 929 of the terminals 92 down, the connecting portions 925 of the terminals 92 deflect and the upper contact points of the terminals 92 move in a horizontal direction. Thus, adjacent portion of the upper contact point of each of the terminals 92 would contact a portion which is not the lower dead point of the solder balls 70, and the force provided for the solder ball 70 is not perpendicular to the bottom of the BGA CPU 7. Therefore, the connections between the solder balls 70 and the terminals 92 are unlikely to be steady and reliable.
In view of the above, a new connector that overcomes the above-mentioned disadvantages is desired.